The goal of the proposed research is to understand how the brain produces the subjective experience of craving in nicotine depending smokers. This compelling urge is implicated in both relapse and maintenance of addicitve. Increased understanding of its neurocognitive mechanisms may suggest new ways to break the cycle of addication and reduce the terrible health cost associated with somking. Two powerful methodologies will be combined to provide convergent evidence. Behavioral laterality experiments will test theoetical and prvious results which suggest that smoking and craving produce assymetric activation of the human cerebral hemispheres. Functional magnetic resonance imaging at 3 Tesla will allow these effects to be localized in the brain with unparalleled spatiotemporal resolution. Both methods will share a common design, allowing the maximum degress of corelation between results. Abstinence from cigarettes produces strong, relable craving, so our basic experimental condition will be to compare the performance of smokers after they have just smoked and after overnight abstinence. To ensure that the observed changes are due to craving and not other symptoms of withdrwanal, we will also study craving induction by environmental cues and resdual craving following nicotine replacement, separating cognitive from pharmacological processes . Data will be correlated with self-reported urge to smoke and blood nicotine assays during each condition, yielding objective brain indicator of subjetive craving.